EP1730405A1

EP1730405A1 - Engine speed-dependent pressure regulation of oil pumps

Info

Publication number: EP1730405A1
Application number: EP04799011A
Authority: EP
Inventors: Dieter Dipl.-Ing. Voigt
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-12-10
Filing date: 2004-11-29
Publication date: 2006-12-13
Also published as: JP2007514097A; US20070111855A1; WO2005057013A1

Abstract

An engine speed-dependent oil pressure regulation of control oil pumps for the lubricant supply of internal combustion engines is ensured by a control piston (1) that hydraulically controls the delivery regulation and to which a differential pressure piston (20) applies a variable additional force. For this purpose, a centrifugal force which is generated in a radial bore (26) of a rotating conveyor wheel (5) of the control oil pump and is variable as a function of engine speed is applied to the differential pressure piston (20).

Description

SPEED ACCELERATED PRESSURE CONTROL OF OLPUMPEN

Field of the invention

The invention relates to the control of the delivery pressure of hydraulic pumps. It relates, in particular, to a speed-dependent pressure regulation of so-called control oil pumps for the lubricating oil supply of internal combustion engines, which have a delivery quantity adjustment device and for their pressurization a control piston for generating a control pressure which is used to vary the delivery pressure of a device with a variable additional force can be applied.

Background of the invention

Hydraulic pumps with a controllable delivery rate have reduced oil pump drive capacities compared with hydraulic pumps with a bypass control and are already being used as so-called control oil pumps with a constantly regulated delivery pressure for supplying lubricating oil to internal combustion engines.

However, it is only through a speed-dependent pressure control of control oil pumps, corresponding to the largely speed-dependent oil pressure requirement of internal combustion engines, that the potential for improvement of control oil pumps can be almost completely utilized. As a result of a then significant reduction in the hydraulic delivery rate, the resulting drive performance advantages of control oil pumps can make a significant contribution to reducing fuel consumption of internal combustion engines.

A control oil pump with variable oil pressure control is known from the patent DE 10237911 B4 and also described in WO 03/058071. In the former case, it is designed as an external gear pump with a displacement unit that executes the displacement adjustment with an axially variable meshing width. The regulation of the operating oil pressure is carried out via the variable flow rate, wherein the axially variable positioning of the displacement unit is adjusted by a regulating pressure acting on it, which is provided by a control piston. The control piston has a control spring and is acted upon counteracting the operating oil pressure, where he works as an oil pressure sensor and is designed for a corresponding desired operating oil pressure. It has control grooves communicating with oil bores, which generate the control pressure for acting on the displacement unit. As a result of an additional, variable application of force to the control piston by a drive device, the operating oil pressure either stepped or continuously adapted to the largely speed-dependent oil pressure demand of the internal combustion engine to be lubricated.

An embodiment of DE 10237911 B4 shows a two-stage switching of the operating oil pressure by a speed-dependent actuated by an acting centrifugal force switching valve. In another embodiment, a continuously variable control of the operating oil pressure by an electrical adjusting device of the control piston, which is controlled by the control unit of the internal combustion engine. A further exemplary embodiment has a spiral groove on a rotating shaft, in which speed-dependent oiling forces produce a pressure acting on the control piston for oil pressure regulation.

While a stepped control of the operating oil pressure only makes limited use of the potential for improvement of a control oil pump, an advantageously stepless control of the operating oil pressure is either associated with an increased electrical control effort or, in the case of spiral pressure control, can only be used within a limited temperature range due to the temperature-variable oil viscosity.

SUMMARY OF THE INVENTION It is the object of the invention to provide an oil pressure control for a control oil pump which continuously adapts the operating oil pressure to the essentially speed-dependent oil pressure requirement of an internal combustion engine without the need for electrical control effort or temperature-related restrictions.

The object is therefore achieved in a second step according to the invention in a simple manner in that the control piston of a control oil pump is acted upon both with operating oil pressure as well as with an additional centrifugal pressure, which is generated dependent on the centrifugal force of an oil column in a rotating radial bore.

Brief description of the drawing

Details of the invention will become apparent from the following description of in

Drawings illustrated schematically illustrated embodiments. Show it:

1 shows an external gear-control oil pump according to the invention with a control piston arranged in the pump housing; 2 shows an oil pressure diagram with the oil pressure requirement of an internal combustion engine and the oil pressure curve of a control oil pump according to the invention;

Fig. 3: an external gear oil pump according to Figure 1, in which the control piston, however, has a decoupled differential pressure piston.

4 shows a section of an external gear oil pump with an arrangement of the oil pressure control according to the invention in its displacement unit;

5 shows an alternative to Figure 4 arrangement of a solenoid valve for oil pressure increase.

Detailed description of the drawing

Fig. 1 shows a first embodiment of an external gear control oil pump according to the invention for an internal combustion engine, in which the oil pressure control is performed by a control piston 1, which is arranged in a pump housing 2. A mounted in a housing cover 3 drive shaft 4 carries a first feed wheel 5, which is in meshing engagement with a second feed wheel 6. The feed wheel 6 is mounted on a stationary pin 7, the right side of the feed wheel 6 a pressure piston 8 and the left side carries a spring piston 9. By an axial displacement of the displacement unit 10, the meshing width of the conveyor wheels 5 and 6 can be varied, whereby a change in the flow rate of the control oil pump possible in a known manner is.

The axial displacement of the displacement unit 10 takes place as a function of the external forces acting on them. While the pressure piston 8 is constantly acted upon by the operating oil pressure acting in its chamber 11, here tapped behind an oil filter 32 as the supply pressure for the internal combustion engine, the force of a restoring spring 12 and a pressure force of a control pressure acting in the spring chamber 13 act on the spring piston 9. The control pressure is generated as required by the control piston 1 in a known manner and fed via a control bore 14 in the spring chamber 13.

The control piston 1 is constantly acted upon at its front-side active surface 15 via its central bore with operating oil pressure. A the operating oil pressure counteracting control spring 16 of the control piston 1 is designed for a certain basic operating oil pressure, for example, 1, 0 bar. By a control pin 17 of the control piston 1, acted upon with operating oil pressure, left-side pressure groove 18 and one with the Environment associated, right-hand relief groove 19, a corresponding control pressure is regulated in the spring chamber 13 in a known manner via the control bore 14. This control pressure sets via the axial positioning of the displacement unit 10, the required for a given nominal operating oil flow rate.

On an oil pressure deviation from the target operating oil pressure, for example, due to a speed change of the internal combustion engine and thereby initially changed pump delivery, the operating as oil pressure sensor control piston 1 reacts with a corresponding axial displacement, so that the pressure prevailing in the spring chamber 13 control pressure is either increased or decreased and a flow adjustment for the purpose of oil pressure correction to the set operating oil pressure.

For a change in the desired operating oil pressure to adapt to the speed-dependent variable oil pressure demand of the internal combustion engine, the control piston 1 is acted upon by an additional force. According to the invention, he has a differential pressure piston 20 for this purpose. While a reference pressure surface 21 of the differential pressure piston 20 is constantly acted upon by a pressure connection 22 with the pressure prevailing in a pressure chamber 23 of the pump housing 2 discharge pressure, is a reference pressure surface 21 opposite centrifugal pressure surface 24 hydraulically via a pressure connection 25 with the inner end of a radial bore 26 of the rotary feed wheel fifth in pressure connection. The radially outwardly ending radial bore 26 in a tooth head of the rotating feed wheel 5 is acted upon by the feed pressure of the pressure chamber 23 in the rotational angle position of feed wheel 5 shown.

The centrifugal force of the oil in the radial bore 26 generates a radially outwardly directed, speed-dependent centrifugal pressure, so that the pressure acting from the pressure chamber 23 to the radial bore 26 discharge pressure is reduced at its radially inner end to the centrifugal pressure. The effective only at the differential pressure piston 20 effective centrifugal pressure, because the both sides acting on him discharge pressure is canceled, exerts on the control piston 1 a control spring 16 supportive, speed-dependent additional force, which also depends on the size of the differential pressure piston 20. This additional force allows only with a correspondingly increased, applied to the active surface 15 operating oil pressure a control function of the control piston 1 for acting in the spring chamber 13 control pressure.

Since arranged in the rotating conveyor wheel 5 radial bore 26 depending on the angle of rotation also with not affected by the delivery pressure areas of the pump housing 2 in Contact comes, for example, with not visible in the representation connection cross-sections of a suction chamber 27, the pressure connection from the radial bore 26 to the centrifugal pressure surface 24 only via a pressure chamber 23 aligned transverse connection 28 of a stationary pin 29 is possible.

By a higher number of radial bores in the conveying wheel 5, for example, one radial bore 26 per conveying tooth, a more effective and even lasting maximum covering effect on the differential pressure piston 20 can be achieved with continuous cross-section with the transverse connection 28.

The two pressure connections 22 and 25 of the differential pressure piston 20 or also the drive pin 29 may contain filters, for example the filters 30 and filters 31, to avoid contamination-related malfunctions.

FIG. 2 shows an oil pressure diagram for an internal combustion engine with an oil supply through the control oil pump shown in FIG. The speed-dependent oil pressure requirement p _{B of} the internal combustion engine, for example, a minimum of 1, 0 bar up to an engine speed n = 2000 / min and then increases with increasing speed parabolic up to 3.7 bar at 6000 / min.

The control spring 16 of the control piston 1 (Fig. 1) is designed for a certain base operating oil pressure po at low speeds without effective Fliehdruckwirkung the differential pressure piston 20, for example, p ₀ = 1, 0 bar as the minimum operating oil pressure for the internal combustion engine.

The resulting in the radial bore 26 centrifugal pressure p _F increases parabolic with the engine speed, but due to the relatively compact dimensions of the feed wheel 5 but at a maximum engine speed of n = 6000 / min as shown in FIG. 2 reaches only about 0.5 bar. However, due to the effective area of the differential pressure piston 20, which is relatively large for the centrifugal pressure p _F , a corresponding amplification factor of V = 6.3 is achieved so that the small centrifugal pressure p _F generated in the radial bore 26 has a sufficiently high additional force on the control piston 1 exercises. This auxiliary force of the differential pressure piston 20, which supports the force of the control spring 16, finally sets the operating oil pressure PR of the internal combustion engine, which is controlled by the control oil pump in accordance with the invention as a function of rotational speed, which is derived from the formula PR = Po + PF x calculated. The operating oil pressure PR must always be greater than the oil pressure requirement PB of the internal combustion engine

A further illustrated in Fig. 3 embodiment of a control oil pump shows over the embodiment in Fig. 1 a modified control piston 41. He has a now axially displaceably guided on him differential pressure piston 42, which from the centrifugal pressure of the radial bore 26 of the feed wheel fifth resulting additional force via a spring 43 and a spring system 44 transmits to the control piston 41.

By now on the spring 43 soft coupling of the differential pressure piston 42 to the control piston 41 only a very small damping effect of the relatively large differential pressure piston 42 is reached, so that the control piston 41 now faster, in contrast to the fixed to the control piston 1 coupled differential pressure piston 20 in Fig. 1, can respond to any deviations from the desired operating oil pressure.

At low speeds without effective centrifugal pressure, the spring 43 is almost powerless relaxed at the differential pressure piston 42 at. When increasing speed with increasing centrifugal pressure, the differential pressure piston 42 moves under increasing bias of the spring 43 to the right, with a corresponding additional force is transmitted to the control piston 41. As a desired consequence, the regulation of the operating oil pressure applied to the active surface 45 now takes place only at a correspondingly increased pressure level in the manner mentioned.

An effective for the differential pressure piston 42 stop 46 limits over a maximum bias of the spring 43, the transferable to the control piston 41 additional force, so that the maximum operating oil pressure is then limited, for example, to 5 bar.

Due to the speed-dependent centrifugal pressure control of the control oil pump, the operating oil pressure can be largely adapted to the oil pressure requirement of an internal combustion engine to be supplied, so that corresponding drive power advantages result from the oil pressure minimization. In special cases increased oil pressure demand of the internal combustion engine, for example, for a quick operation of a hydraulic camshaft adjuster can be achieved by a controlled by an engine control unit solenoid valve 47, a pressure relief at the normally acted upon by centrifugal centrifugal pressure surface 48 of the differential pressure piston 42. The delivery pressure which always acts on the reference pressure surface 49 of the differential pressure piston 42 then pushes the differential pressure piston 42 against its abutment 46, so that the spring 43 is pretensioned to a maximum extent and then an independently controlled speed an increased operating oil pressure of, for example, 5 bar. A throttle 50 located in the pressure connection 25 causes a more effective pressure reduction at the centrifugal pressure surface 48 of the differential pressure piston 42 when the solenoid valve 47 is actuated.

As an alternative to the arrangement of the control piston according to the invention in the pump housing according to the embodiments of Figures 1 and 3 in an external gear oil pump also an arrangement of the control piston within the adjusting the displacement adjustment making displacement unit is possible. As a result, a very compact trained control oil pump with a simple pump housing executable. 4 shows a preferred embodiment of a displacement unit 60 in an enlarged section of an external gear oil pump.

The displacement unit 60 has a feed wheel 61 with a centrifugal pressure generating, arranged obliquely to the centrifugal force radial bore 62. The feed wheel 61 is rotatably mounted on a hollow pin 63, which is integrally formed with a spring piston 64. The axial position of the displacement unit 60 and thus the respective delivery rate of the external gear oil pump is on the one hand by the pressure acting on the pressure piston 65 in its chamber 66 operating oil pressure and on the other by counteracting Force on the spring piston 64 dependent, which are generated on the one hand by a return spring 67 and on the other by the force acting in its spring chamber 68 control pressure.

The control pressure is generated in this embodiment by an arranged in the pin 63 annular control piston 69. On the one hand, it is acted upon by the operating oil pressure acting in the chamber 66 and, on the other hand, it is supported by a control spring 70. It rests against a collar 71 of a pressure tube 72, which feeds the control pressure generated by the control piston 69 into the spring chamber 68 via its central bore 74. The collar 71 on the pressure tube 72 is supported on a cover 73 fixed in the spring piston 64. The pressure pipe 72 penetrates the control piston 69 sealingly with a sliding seat. Its central bore 74, which is closed at its end facing the chamber 66, is constantly in pressure communication with a groove 75 of the control piston 69, for example via corresponding transverse bores in the pressure pipe 72 and in the control piston 69. The groove 75 of the control piston 69 is in the shown, middle control position simultaneously with a supplied with operating oil pressure from the chamber 66 pressure bore 76 as well as with a discharge hole 78 which is connected to a suction chamber 77, slightly in overlap. Deviations from the desired operating oil pressure, which acts on the end face of the control piston 69 from the chamber 66, are automatically corrected by axial control movements of the control piston 69 in the manner already mentioned about acting in the spring chamber 68 control pressure by an axial displacement of the displacement controlling the displacement unit 60 ,

In the spring piston 64, a differential pressure piston 79 is arranged, which is axially movably mounted on a guide sleeve 80 in the cover 73 and the pivot pin 63 and according to the invention via a spring 81 elastically an additional force can be transmitted to the control piston 69. The in a pressure pocket 82 of the spring piston 64 constantly acting delivery pressure of the control oil pump is on the one hand via a connection 83 of the spring piston 64 and on the other via the oblique radial bore 62 of the feed wheel 61, a directed

Transverse bore 84 in the pin 63 and local radial clearance between the guide sleeve 80 and the pin 63 in principle on both sides of the differential pressure piston 79 at. However, this delivery pressure is reduced in the radial bore 62 by the centrifugal pressure which acts as a function of the rotational speed, so that effectively only the centrifugal pressure generates an additional force on the differential pressure piston 79.

This additional force generated by the differential pressure piston 79 is limited in its abutment against a stop 85 by a then maximum bias of the spring 81, so that the adjusted, highest operating oil pressure of the control oil pump is then limited, for example to 5 bar.

In order to achieve a perfect function of the control, the cavities in the pin 63 must be pressure-free. For this purpose, the pressure piston 65 a with the suction chamber 77 in communication standing suction pocket 86, which causes a relief bore 87 of the stud 63, the pressure relief of these cavities.

A temporary increase in the operating oil pressure with increased oil pressure requirement of the internal combustion engine is also possible with an arrangement of the control piston 69 in the displacement unit 60. For this purpose, a line 88, which is under operating oil pressure, has a solenoid valve 89 which, when electrically actuated by the engine control unit via a throttle bore 90, carries out a pressure increase superimposed on the control pressure of the spring chamber 68. As a result, the displacement unit 60 of the return spring 67 to the right pushed into a position of increased oil flow with resulting increase in the operating oil pressure. However, a pressure relief valve 91 limits the pressure in the spring chamber 68 to a certain value, so that the operating oil pressure acting in the chamber 66 can only increase to a corresponding maximum value. In this then speed-independent, maximum operating oil pressure, the control oil pump continues to work with active flow control, the control piston 69 is then no function.

FIG. 5 shows, as an alternative to FIG. 4, a further possible embodiment of an external gear control oil pump with a centrifugal pressure control integrated in the displacement unit 60. In a the operating oil pressure in the chamber 66 feeding feed line 92, a solenoid valve 93 is arranged, which is closed at a predetermined by the engine control unit raising the operating oil pressure and simultaneously depressurized via a nozzle 94, the chamber 66. The return spring 67 then moves the displacement unit 60 to the position of maximum flow rate with a resulting increase in the operating oil pressure. Because of the then inactive flow rate control, however, a conventional bypass control with a pressure relief valve 95 is now required to limit the maximum operating oil pressure to, for example, 6 bar.

In FIG. 5, in contrast to FIG. 4, the control piston 69, which is acted upon by operating oil pressure from the chamber 66, only supports itself via a prestressed control spring 97 on the differential pressure piston 79.

However, this simplified version has a somewhat different control characteristic compared with the embodiment in FIG. 4, since the additional force generated at the differential pressure piston 79 by centrifugal pressure can only influence the pressure regulation above a certain operating speed when the pretensioning force of the control spring 96 is overcome.

An oil-filled throttle chamber 97 formed between the cover 73 of the guide sleeve 80 of the differential pressure piston 79 and the collar 71 of the pressure tube 72 can steam the movement of the differential pressure piston 79 with a suitable choice of play between the guide sleeve 80 and the collar 71. In this way, in particular a transmission of the rapid control movements of the control piston 69 is avoided by its elastic coupling to the differential pressure piston 79, so that it remains almost unchanged in position with appropriate damping, thus enabling a stable control function. The control device according to the invention utilizes the centrifugal force caused by centrifugal force centrifugal pressure in the oil-filled radial bores of rotating components for speed-dependent oil pressure control of control oil pumps. As a result, a consumption-advantageous reduction of the oil pump drive power for internal combustion engines is achieved in a simple manner at all operating temperatures.

Claims

1. Speed-dependent pressure control for hydraulic pumps, in particular for control oil pumps with a delivery quantity adjustment device for supplying lubricating oil to internal combustion engines, with a control piston (1, 41, 69) and a control spring (16, 70, 96) for generating a control pressure for pressurizing the delivery rate adjustment device (10, 60) and with a device for generating an additional force acting on the control piston (1, 41, 69), characterized in that the additional force is applied by a differential pressure piston (20, 42, 79), which is operated by a at least one oil-filled radial bore (26, 62) of a rotating component (5, 61) is subjected to centrifugal pressure acting as a function of speed.

2. Speed-dependent pressure control for hydraulic pumps according to claim 1, characterized in that the radial bore (26, 62) has at least one of the following features: (a) it is arranged in a feed wheel (5, 61) of the control oil pump in the direction of the centrifugal force or at an angle thereto; (b) at its outer end it is acted upon by delivery pressure from a pressure chamber (23) or a pressure pocket (82) in certain rotational angle positions of the feed wheel (5, 61).

3. Speed-dependent pressure control for hydraulic pumps according to one of the preceding claims, characterized in that the differential pressure piston (20, 42, 79) has at least one of the following features: (a) it is on the one hand via at least one pressure connection (22, 83) Conveying pressure and on the other hand acted upon with a delivery pressure reduced by the centrifugal pressure; (b) it is formed in one piece with the control piston (1) and transmits the additional force directly to the control piston (1); (c) it is designed to be axially movable to the control piston (1) and transmits the additional force to the control piston (41, 69) via a control spring (43, 81, 97); (d) it has a throttle chamber (97).

4. Speed-dependent pressure control for hydraulic pumps according to one of the preceding claims, characterized in that the control piston (1, 42, 69) has at least one of the following features: (a) it has a control spring (16, 72) and one acting in the same direction Spring (43, 81) for the differential pressure piston (42, 79), the spring (43, 81) preferably relieved without pressure of the differential pressure piston (42, 79) and at maximum pressure force of the differential pressure piston (42, 79) by its stop (46, 85) is force limited; (b) it has a control groove (75) which, in the control position, has a slight overlap on the one hand with a pressure bore (76) and on the other hand with a relief bore (78); (c) it is supported by a control spring (96) exclusively on the differential pressure piston (79); (d) it is formed in one piece with the differential pressure piston (20).

5. Speed-dependent pressure control for hydraulic pumps according to one of the preceding claims, characterized in that the pressure connection to the differential pressure piston fulfills at least one of the following features: (a) the pressure connection from the radial bore (26, 62) to the differential pressure piston (20, 42, 79)) takes place via a transverse connection (28, 84) of a stationary running pin (29, 63) of the feed wheel (5, 61) aligned with the pressure chamber (23) or the pressure pocket (82); (b) the pressure connection (22, 25) to the differential pressure piston (42) has a filter (30, 31); (c) the pressure connection (22, 25) to the differential pressure piston (20, 42) has a throttle (50).

6. Speed-dependent pressure control for hydraulic pumps according to one of the preceding claims, characterized in that in an external gear control oil pump, the control piston (69, 96) as well as the differential pressure piston (79) within a displacement unit (60) with a return spring (67) in a spring chamber (68) formed delivery rate adjustment device are arranged.

7. Speed-dependent pressure control for hydraulic pumps according to one of the preceding claims, characterized in that the control piston (69) arranged in the displacement unit (60) is in pressure connection with the spring chamber (68), and that at least one of the following features is preferably provided : a) the pressure connection runs over a pressure pipe (72) penetrating a cover (73) of the displacement unit (60); b) the spring chamber (68) can be acted upon by a solenoid valve (89) with oil pressure via a throttle bore (90); c) the spring chamber (68) is pressure-limited by a pressure relief valve (91).

8. Speed-dependent pressure control for hydraulic pumps according to one of the preceding claims, characterized in that the pressure acting in the chamber (66) on the displacement unit (60), preferably by means of a solenoid valve (93), can be switched off.

9. Speed-dependent pressure control for hydraulic pumps according to one of the preceding claims, characterized in that the centrifugal pressure surface (48) of the differential pressure piston (42) can be relieved of pressure by a solenoid valve (47).